How severe is CVE-2023-6866?

CVE-2023-6866 has a CVSS 3.x base score of 8.8, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2023-6866 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (48th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2023-6866?

CVE-2023-6866 affects Mozilla Firefox. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2023-6866?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

When was CVE-2023-6866 published?

CVE-2023-6866 was published on 2023-12-19 and last updated on 2026-06-17.

CVE-2023-6866

CVE-2023-6866 is a high-severity vulnerability in Mozilla Firefox with a CVSS 3.x base score of 8.8. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-755.

Key facts

Severity: High (CVSS 3.x base score 8.8)
EPSS exploit prediction: 1% (48th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-755
Affected product: Mozilla Firefox
Published: 2023-12-19
Last modified: 2026-06-17

Description

TypedArrays can be fallible and lacked proper exception handling. This could lead to abuse in other APIs which expect TypedArrays to always succeed. This vulnerability affects Firefox < 121.

Frequently asked questions

What is CVE-2023-6866?: TypedArrays can be fallible and lacked proper exception handling. This could lead to abuse in other APIs which expect TypedArrays to always succeed. This vulnerability affects Firefox < 121.
How severe is CVE-2023-6866?: CVE-2023-6866 has a CVSS 3.x base score of 8.8, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2023-6866 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (48th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2023-6866?: CVE-2023-6866 affects Mozilla Firefox. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2023-6866?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
When was CVE-2023-6866 published?: CVE-2023-6866 was published on 2023-12-19 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:mozilla:firefox:*:*:*:*:*:*:*:*

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